Four new beta adrenergic blocking agents carrying tyramine as the amino moiety were synthesized and the distribution of their I-125-radioiodinated derivatives evaluated in rats. A derivative of a nonspecific blocker, alprenolol showed poor blood clearance and no cardiac selectivity. A derivative of a cardio-selective blocker, practolol, showed a promising heart/blood ratio (approximately 19) and cardioselectivity with a heart/lung ratio of approximately 2. Two additional practolol analogs did not show any improvement over the practolol derivative. Because of the increased lipophilicity of the derivatives, blood clearance and cardioselectivity were diminished. We conclude that polarity plays an important role in blood clearance and cardioselectivity of these beta adrenoceptor blocking agents.